The present invention relates to a laser warning device. In a military connection, such devices have the task to register laser radiation from e.g. laser rangefinders or laser designators and by a warning signal make clear to the illuminated person that laser illumination has occurred or continues. The laser warning device can be located on or in close vicinity of military objects that are especially exposed to systems using a laser for target acquisition and the like, for instance tanks, ships and permanent installations, such as airfields etc. Laser beams for the mentioned reasons have very little divergence. Typically the cross-section of the main beam is 1 m after 1 km. It could therefore be necessary to place several laser warning devices in different places around an object in order to get a reasonable security of detection, if the object is large. Due to the atmospheric conditions there is also a weeker more or less scattered radiation of considerably greater cross-section.
The laser warning device shall indicate that laser illumination has occurred and it is also desirable that it is able to establish the direction (bearing and elevation) and the type of laser (laser wavelength, pulse length and pulse repetition frequency).
There are several previous types of laser warning devices. Most of them require a great number of light collection elements or detectors in order to determine the direction to the light source with high resolution. That what is shown in the German Offenlegungsschrift 3 300 849, U.S. Pat. No. 4,868,378 and the Swedish Patent 459 529 can be mentioned as examples. They all have different drawbacks.